This is an electrolytic 400 vdc 12,000uF capacitor capable of discharging 960J of energy. It is approximately 12″ in height with a 3″ diameter base.
Discharge onto a 1/16″ aluminum plate. The discharge left two vaporized patches, each roughly 1″ in diameter.
Discharge into a 2″ cluster of steel wool.
Discharge onto four layers of aluminum foil.
Videos of several 1kJ capacitor discharges: